Dialkyl-peroxydicarbonates are mainly used in the polymerization industry as initiators for ethylenically unsaturated polymerizable compounds, particularly as initiators for the polymerization of vinyl chloride. Dialkyl-peroxydicarbonates are relatively unstable compounds and at a certain temperature they decompose forming free radicals which start the polymerization. The decomposition temperature varies with the chain length of the alkyl groups and short-chain dialkyl-peroxy-dicarbonates, e.g. diethyl- or di-isopropyl-peroxydicarbonates decompose explosively at about 25.degree. C and must therefore be cold stored. Peroxydicarbonates having higher alkyl groups (also including cyclic derivatives) are more stable but certain precautions must likewise be taken in storing and handling of these. The lower peroxydicarbonates are liquid and are charged as such or dissolved in a solvent during the polymerization while the higher peroxydicarbonates are solid and are charged to the polymerization reactor in the form of powder. The recent development in vinyl chloride polymerization technique, change-over to very large polymerization autoclaves and computerized process control and the discovered environmental problems of the noxiousness of vinyl chloride, has made handling of the dialkyl-peroxydicarbonates in the form of dispersions desirable. Charging of the initiator by pumping into the reactor without necessity of opening it means that the polymerization operators avoid contact with vinyl chloride.
Liquid dialkyl-peroxydicarbonates, i.e. such having shortchain alkyl groups, are easily brought into dispersion by agitation in a cold mixture of water and emulsifier. The solid peroxydicarbonates have the disadvantage of being difficult to bring into aqueous dispersion without reducing the active peroxide content, which involves decreasing the efficiency of the peroxydicarbonates as initiators. Dispersing solid dialkyl-peroxydicarbonates in water by means of e.g. turbine agitators, colloid mills, pressure homogenizers or ball mills does give dispersions, but these show reduced active peroxide content of the solid peroxydicarbonate.